Abstract: OBJECTIVE: A variety of pharmacologic therapies are available or in development for the prevention of breast cancer recurrence. Assessing the value of these treatments is compromised by a paucity of data on the impact of recurrence on economic costs and survival. The purpose of this study was to shed light on these issues. METHODS: We conducted a retrospective analysis of linked SEER-Medicare data. All patients in the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) registry who were diagnosed with nonmetastatic breast cancer during 1991-1993 were identified, and their subsequent Medicare claims were scanned for evidence of further breast cancer events (local or distant recurrence, contralateral breast cancer). Medicare claims were then scanned from the time of the event through 2002 to assess patterns of survival and costs. RESULTS: We identified 10,798 patients in SEER who were diagnosed with nonmetastatic breast cancer during 1991-1993, including 1833 who subsequently had another breast cancer event (local recurrence, 958; distant recurrence, 622; contralateral breast cancer, 253). Median survival was 37 months and 8 months among patients with local and distant recurrence, respectively; 53% of patients with contralateral breast cancer remained alive after all the data were censored at 97 months. Expected 10-year costs (2004 US$, discounted 3%) attributable to distant recurrence, local recurrence, and contralateral breast cancer were $11,450 (SE 2056), $19,596 (SE 1754), and $19,183 (SE 4131), respectively. CONCLUSION: Breast cancer recurrence and contralateral breast cancer lead to substantial increases in costs, amounting to approximately $11,000-19,000 over 10 years depending on type. The impact of these events on survival also varies considerably by type.